Heterocyclic-2-thione derivatives of silver(I): Synthesis, spectroscopy and structures of mono- and di-nuclear silver(I) halide complexes

• The C:N ratio of core rings reveal the nature of bridging between two silver atoms.
• The substituents at N atom alter silver–silver contact.
• The rupture of silver-halogen bonds by dithiouracil is rare feature.

The scarcely known chemistry of silver(I) halides with a series of heterocyclic thiones in acetonitrile (or methanol–acetonitrile) is described. Silver(I) chloride with a series of imidazolidine-2-thiones [C3H5NS(N–R)] in the presence of one equivalent of PPh3 with respect to the thione ligand has yielded chloro-bridged dinuclear complexes, [Ag2(μ-Cl)2(κ1-S-C3H5NS(N–R))2(PPh3)2] (1, R = H; 2, R = Me; 3, R = Et), and in the presence of two equivalents of PPh3, it has yielded mononuclear complexes, [Ag(κ1-Cl)(κ1-S-C3H5NS(N–R))(PPh3)2] (4, R = Me; 5, R = Et). The n-propyl-imidazolidine-2-thione with silver(I) chloride formed only a mononuclear complex, [Ag(κ1-Cl)(κ1-S-C3H5NS(N–Prn))(PPh3)2] (6), in the presence of one or two equivalents of PPh3. In contrast, silver(I) bromide with C3H5NS(N–R) in the presence of one or two equivalents of PPh3 with respect to the thione ligand has yielded bromide-bridged dinuclear complexes, [Ag2(μ-Br)2(κ1-S-C3H5NS(N–R))2(PPh3)2] (7, R = Me; 8, R = Et; 9, R = Prn). The related thio-ligands, namely, 1-methyl-imidazoline-2-thione and thiazolidine-2-thione with silver(I) bromide in the presence of one or two equivalents of PPh3 have formed bromide bridged dimeric [Ag2(μ-Br)2(κ1-S-C3H3NS(N–Me))2(PPh3)2] (10) or mononuclear Ag(κ1-Br)(κ1-S-C3H5NS2)(PPh3)2] (11) complexes respectively. The 2,4-dithiouracil (C4H4N2S2) with silver(I) chloride/bromide and PPh3 has yielded hetero-bridged dinuclear complexes, [Ag2(μ-S,S-C4H3N2S2)(μ-X)(PPh3)4] (X = Cl, 12; Br, 13) involving rupture of Ag–X bonds directly with a thio-ligand, a rare case of such rupture in metal-heterocyclic thione chemistry.

A series of mono- and di-nuclear silver(I) halide complexes with heterocyclic thiones in the presence of a tertiary phosphine co-ligand have been investigated. High C:N ratio of the heterocyclic ring favors sulfur bridging while low C:N ratio favors halogen bridging. 2,4-Dithioural has shown rare splitting of silver(I)-halogen bond (12).Figure optionsDownload as PowerPoint slide